Preparation of zirconia–ceria powders by coprecipitation of a mixed zirconium carbonate in water with urea

Ceria zirconia precursors were obtained by applying the urea hydrolysis method to Zr–oxychloride and Ce–nitrate solutions. Dewatering–dying procedures, such as freeze drying (FD) and acetone–toluene–acetone (ATA), were compared with the usual thermal method to assess their suitability for yielding fine, aggregate–free powders for the preparation of ceria–zirconia sinters. The characteristics of the powders before and after calcinations are discussed. The advantage of the ATA method is based on the fact that the formation of hard agglomerates is avoided, high specific surface is achieved and the tetragonal form was the only phase crystallizing on calcination of the chemical precursor.